Scilab Textbook Companion for Electrical Machine Design by A. K. Sawhney1 Created by Shiv Singh Meena B.Tech Electrical Engineering National Institute of Technology,Kurukshetra College Teacher None Cross-Checked by None July 31, 2019 1Funded by a grant from the National Mission on Education through ICT, http://spoken-tutorial.org/NMEICT-Intro. ThisTextbookCompanionandScilab codes written in it can be downloaded from the ”Textbook Companion Project” section at the website http://scilab.in Book Description Title: Electrical Machine Design Author: A. K. Sawhney Publisher: Dhanpat Rai Edition: 6 Year: 2014 ISBN: 9788177001013 1 Scilab numbering policy used in this document and the relation to the above book. Exa Example (Solved example) Eqn Equation (Particular equation of the above book) AP Appendix to Example(Scilab Code that is an Appednix to a particular Example of the above book) Forexample, Exa3.51meanssolvedexample3.51ofthisbook. Sec2.3means a scilab code whose theory is explained in Section 2.3 of the book. 2 Contents ListofScilabCodes 4 3 Principles of Magenetic Circuit Design 5 4 Thermal Design Aspects of Electrical Machines 20 5 Design of Transformers 51 6 General Concepts and Constraints in Design of Rotating Machines 67 7 Armature Windings 75 8 Aspects of Design of Mechanical Parts 80 9 DC Machines 85 10 Three Phase Induction Motors 98 11 Design of Synchronous Machines 106 15 Design of Magnetic Circuits 121 3 16 Design of Heating Elements and Inductors and Welding Transformers 125 18 Design of Starters and Field Regulators 127 4 List of Scilab Codes Exa 3.1 Calculating effective length of air gap . . . . 5 Exa 3.2 Calculating the mmf required for the air gap of a machine . . . . . . . . . . . . . . . . . . 6 Exa 3.3 Estimating the effective air gap area per pole 7 Exa 3.4 Estimating the average flux density in the air gap . . . . . . . . . . . . . . . . . . . . . . . 9 Exa 3.7 Calculating the apparent flux density . . . . 11 Exa 3.8 Calculating the apparent flux density . . . . 12 Exa 3.11 Calculating the specific iron loss . . . . . . . 13 Exa 3.12 Calculating the specific iron loss . . . . . . 14 Exa 3.13 Calculating the hysteresis loss . . . . . . . . 16 Exa 3.15 Calculatingthemagneticpullandunbalanced magnetic pull and ratio of unbalanced mag- netic pull to useful force . . . . . . . . . . . 18 Exa 4.1 Calculating the loss that will pass through copper bar to iron . . . . . . . . . . . . . . 20 Exa 4.2 Calculating the loss that will be conducted across the the laminations . . . . . . . . . . 21 Exa 4.3 Calculating the heat radiated from the body 22 Exa 4.4 Calculating the length and width of strip . . 23 Exa 4.6 Estimating the temperature of the hot spot 25 Exa 4.7 Estimating the hot spot temperature . . . . 26 Exa 4.8 Calculatingthemaximumtemperaturediffer- ence between the coil surface and the winding 27 Exa 4.9 Calculatingthetemperaturedifferencebeetween the centre of the embedded portion of a con- ductor and the overhang . . . . . . . . . . . 29 5 Exa 4.11 Calculatingtheheatconductedacrossthefor- mer from winding to core . . . . . . . . . . 30 Exa 4.12 Estimating the final steady temperature rise of coil and its time constant . . . . . . . . . 31 Exa 4.13 Calculating the final steady temperature rise of coil surface and hot spot temperature rise 33 Exa 4.15 Calculating the temperature rise and thermal time constant and rating of the machine . . 34 Exa 4.17 Calculating the temperature of machine after one hour of its final steady temperature rise 36 Exa 4.19 Calculating the rate of change of temperature 37 Exa 4.22 Calculating the volume of air required per second and fan power . . . . . . . . . . . . . 38 Exa 4.23 Calculatingtheefficiencyofmachineandamount of cooling water . . . . . . . . . . . . . . . . 40 Exa 4.24 Calculating the temperature rise of hydrogen 41 Exa 4.25 Calculating the amount of oil and amount of water . . . . . . . . . . . . . . . . . . . . . 42 Exa 4.26 Calculating the temperature rise of tank . . 44 Exa 4.27 Calculatingtheamountofwaterrequiredand area of water duct and pumping power . . . 45 Exa 4.35 Calculating the continuous rating of motor . 47 Exa 4.37 Calculating the mean temperature rise . . . 48 Exa 4.43 Calculating the temperature rise . . . . . . 49 Exa 5.3 Calculating the kVA output of a single phase transformer . . . . . . . . . . . . . . . . . . 51 Exa 5.6 Calculatingthenetironareaandwindowarea and full load mmf . . . . . . . . . . . . . . . 52 Exa 5.9 Calculating the net iron area and window area 54 Exa 5.12 Calculating the resistance of secondary wind- ing . . . . . . . . . . . . . . . . . . . . . . . 55 Exa 5.13 Calculatingtheleakagereactanceofthetrans- former referred to the HV side . . . . . . . . 56 Exa 5.14 Calculating the per unit leakage reactance . 58 Exa 5.16 Calculating the instantaneous radial force on the HV winding if a short circuit occurs at the terminals of the LV winding with HV en- ergised and the force at full load . . . . . . . 60 6 Exa 5.17 Calculatingtheinstantaneousradialforceand instantaneous axial force on the HV winding under short circuit conditions . . . . . . . . 61 Exa 5.18 Calculating the maximum flux and no load current of the transformer . . . . . . . . . . 62 Exa 5.20 Calculating the number of turns and no load current . . . . . . . . . . . . . . . . . . . . . 65 Exa 6.1 Calculating the specific electric and specific magnetic loading . . . . . . . . . . . . . . . 67 Exa 6.5 Calculating the power developed by the ar- mature of motor . . . . . . . . . . . . . . . 68 Exa 6.6 Calculatingthelimitingvalueofspecificmag- netic loading . . . . . . . . . . . . . . . . . 70 Exa 6.8 Calculatingthemaximumpermissiblespecific electric loading . . . . . . . . . . . . . . . . 71 Exa 6.9 Calculating the specific electric loading . . . 72 Exa 7.33 Calculating the rms line voltage and circulat- ing current . . . . . . . . . . . . . . . . . . 75 Exa 7.41 Calculating the eddy current loss ratio and average loss ratio and critical depth for min- imum loss . . . . . . . . . . . . . . . . . . . 76 Exa 8.2 Calculating the stress on the ring . . . . . . 80 Exa 8.4 Calculating the tensile stress and factor of safety . . . . . . . . . . . . . . . . . . . . . 81 Exa 8.5 Calculating the inertia constant of the gener- ator . . . . . . . . . . . . . . . . . . . . . . 83 Exa 9.7 Calculatingthemaximumpermissiblecorelength for the machine . . . . . . . . . . . . . . . . 85 Exa 9.8 Calculating the maximum permissible output from a machine . . . . . . . . . . . . . . . . 86 Exa 9.9 Calculating the number of extra shunt field turns to neutralize the demagnetization . . . 87 Exa 9.10 Calculatingthedemagnetizingandcrossmag- netizing mmf per pole . . . . . . . . . . . . 89 Exa 9.12 Calculating the armature voltage drop . . . 90 Exa 9.26 Calculatingthenumberofturnsoneachcom- mutating pole . . . . . . . . . . . . . . . . . 91 7 Exa 9.27 Calculating the reactance voltage for a ma- chine with straight line and sinusoidal com- mutation . . . . . . . . . . . . . . . . . . . . 92 Exa 9.32 Calculating the minimum number of poles . 94 Exa 9.33 Calculating the maximum armature voltage 95 Exa 9.34 Calculating the total commutator losses . . 96 Exa 10.2 Calculating the main dimentions of squirrel cage induction motor . . . . . . . . . . . . . 98 Exa 10.13 Calculating the number of stator and rotor turns and rotor voltage between slip rings at standstill . . . . . . . . . . . . . . . . . . . 99 Exa 10.15 Calculating the number of stator turns per phase . . . . . . . . . . . . . . . . . . . . . 101 Exa 10.16 Calculating the magnetizing current per phase 103 Exa 10.19 Calculating the current in rotor bars and in end rings . . . . . . . . . . . . . . . . . . . 104 Exa 11.4 Calculating the suitable number of slots and conductors per slot . . . . . . . . . . . . . . 106 Exa 11.10 Calculating the size of armature wire and the ac resistance of each pahase . . . . . . . . . 107 Exa 11.11 Calculating the length of air gap . . . . . . 109 Exa 11.13 Calculating the stator bore and stator core lengthandturnsperphaseandarmaturemmf per pole and mmf for air gap and field current 111 Exa 11.14 Calculating the flux per pole and length and width of pole and winding height and pole height . . . . . . . . . . . . . . . . . . . . . 114 Exa 11.18 Calculating the direct and quadrature axis synchronous reactances . . . . . . . . . . . . 115 Exa 11.20 Calculating the kVA output of the machine 117 Exa 11.32 Calculatingthenumberofstatorslotsandav- erage flux density . . . . . . . . . . . . . . . 119 Exa 15.1 Calculating the current in exciting coil . . . 121 Exa 15.4 Calculating the winding depth and winding spaceandspacefactorandthenumberofturns 122 Exa 16.2 Calculating the inductance . . . . . . . . . . 125 8 Exa 18.1 Calculating the upper and lower limits of cur- rent during starting and resistance of each section . . . . . . . . . . . . . . . . . . . . . 127 9